A225348 Number of 8Xn -1,1 arrays such that the sum over i=1..8,j=1..n of i*x(i,j) is zero, the sum of x(i,j) is zero, and rows are nondecreasing (number of ways to distribute n-across galley oarsmen left-right at 8 fore-aft positions so that there are no turning moments on the ship)

8, 77, 410, 1525, 4508, 11291, 25056, 50659, 95130, 168289, 283338, 457627, 713374, 1078615, 1587974, 2283803, 3217102, 4448769, 6050622, 8106883, 10715232, 13988475, 18055740, 23064277, 29180742, 36593245, 45512628, 56174753, 68841880

Offset

1,1

Comments

Row 8 of A225345

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = a(n-1) +a(n-2) -a(n-5) -a(n-7) -a(n-8) +a(n-10) +a(n-11) +2*a(n-12) -2*a(n-16) -a(n-17) -a(n-18) +a(n-20) +a(n-21) +a(n-23) -a(n-26) -a(n-27) +a(n-28)

Example

Some solutions for n=4
.-1..1..1..1...-1..1..1..1...-1..1..1..1...-1..1..1..1...-1.-1..1..1
.-1..1..1..1...-1..1..1..1...-1.-1.-1.-1...-1.-1..1..1...-1.-1.-1..1
.-1.-1..1..1...-1.-1..1..1...-1..1..1..1...-1..1..1..1...-1..1..1..1
.-1.-1.-1.-1...-1.-1.-1.-1...-1.-1.-1..1...-1.-1.-1.-1...-1.-1.-1..1
.-1.-1.-1.-1...-1.-1.-1..1...-1.-1..1..1...-1.-1.-1..1....1..1..1..1
.-1..1..1..1...-1.-1.-1..1...-1..1..1..1...-1.-1..1..1...-1.-1..1..1
.-1.-1.-1..1...-1.-1..1..1....1..1..1..1...-1.-1.-1..1...-1.-1.-1..1
..1..1..1..1....1..1..1..1...-1.-1.-1.-1....1..1..1..1...-1.-1..1..1

Crossrefs

Sequence in context: A024281 A232087 A105429 * A091686 A091691 A024103

Adjacent sequences: A225345 A225346 A225347 * A225349 A225350 A225351

Keyword

nonn

Author

R. H. Hardin May 05 2013

Status

approved